The aim and purpose of this research is the development of economically justifiable systems for crossflow micro- and ultrafiltration that reduce or eliminate the effects of concentration and gel polarization on permeate flux thereby increasing the efficiency. The objects required to achieve this aim are: l. Evaluate and compare the relative benefits and disadvantages of pulsed flow and reversing pulsed flow in various crossflow channel configurations in order to provide effective design scaling data. 2. Perform a careful, detailed economic analysis that will compare the performance benefits versus anticipated increases or decreases) in construction and maintenance costs for selected applications. 3. Based on data and decisions resulting from the first and second objectives, design and build a demonstration system for independent evaluation. This evaluation will be conducted at the Virginia Center for Biotechnology located on the campus of Virginia Polytechnic and State University and one or both of the two local biotechnology companies that will be advising and collaborating on this Phase II effort.